The present application relates generally to systems, and apparatus for improving the efficiency and operation of turbine engines, which, as used here and unless specifically stated otherwise, is meant to include all types of turbine or rotary engines, including steam turbine engines, combustion turbine engines, aircraft engines, power generation engines, and others. More specifically, but not by way of limitation, the present application relates to systems, and apparatus pertaining to turbine engine diaphragms and shells.
Turbine engines, such as steam turbines or gas turbines, typically include multiple turbine stages with each stage including a pair of interspersed stator rings and rotors. The stator rings (diaphragms) include nozzles or stator airfoils, and the rotors include buckets or rotating airfoils. To rotate the rotor, the nozzles direct high pressure and high temperature fluid onto the buckets in a direction that causes the buckets to rotate with a speed proportional to the fluid pressure.
To support the diaphragms and for maximum fluid utilization, the typical turbine engine includes one or more outer shells or casings. The outer shell isolates the working fluid from the ambient conditions outside the turbine engine, and also supports and provides alignment to the diaphragms. As the shell structures are constantly exposed to high pressures and temperatures, these structures are typically made from good quality and high-grade alloy metals that can withstand high pressures and temperatures; the higher the fluid's working pressure and temperature, the thicker the shell structure, and the better the metal quality. So, for very high pressure and temperature applications, turbine engines include three or more concentric shell structures. Each shell structure provides a layer of isolation from the temperature and pressure inboard of that shell, thereby splitting up the pressure and temperature change. As the inner most shell structure is subjected to the highest temperatures and pressures, this shell structure is the thickest and made from very expensive high-alloy steel; the outer shells, however, are exposed to intermediate pressures and temperatures, and therefore these structures are relatively thinner and made from lighter metals.
To reduce costs, attempts have been made to remove one or more shell structures. One such attempt removes the inner shell, leaving only the outer shell both to support the diaphragm and to contain the pressure and temperature within the turbine engine. That structure, however, provides only limited utility in high temperature and pressure applications, as the outer shell cannot, by itself, contain the high fluid pressure and temperature. Further, as only one shell structure is utilized the shell is thicker as compared to the outer shells utilized in three shell structures. The shell is cast from very expensive high-alloy steel, which again results in very expensive designs.
As a result, there remains a need for innovative approaches to more efficient and cost effective shell structures and diaphragms for turbine engines.